This invention relates to a slow-acting rotation shaft device which rotatably supports first and second rotative portions which rotate relatively to a fixed member.
As a switch device having two rotative members which thus independently rotate, there exists a case for a compact disc, a compact case for toiletries or the like, and these are used for a rotatably supporting portion of the two rotative shaft members in the slow-acting rotation shaft of this invention.
A conventional switch device having two rotative members which rotate independently is used with only one rotative member of the slow-acting rotation shaft device as shown in FIG. 8(a) and (b).
In FIG. 8(a) and (b), the switch device is incorporated so that first and second members 1a and 2a may relatively rotate with respect to a fixed member 2. In this case, the slow-acting rotation shaft device is constructed by a shaft 3 incorporated at the rotatably supporting portion of each rotative member 1a and 1b.
This shaft body 3 comprises a hollow shaft body 31, cap members 32 and 33 outwardly inserted rotatably at both sides of the shaft body 31, a torsion bar 4 which latches one end hook portion thereof in the shaft body 31 and another hook portion 42 thereof in the cap member 33, and a viscous grease (not shown) enclosed between the shaft body 31 and the cap members 32, 33.
The shaft body 31 is formed by a stepped shaft having small diameter portions 31b, 31b at both sides of a large diameter shaft portion 31 positioned at a central portion thereof, said small diameter portions 31b, 31b being outwardly inserted cap members 32 and 33 rotatably. Further, a slit penetrated hole 34 is format in a longitudinal direction and a key 35 is protruded at a large shaft portion 31a.
Each of the cap members 32 and 33 is provided with a cylinder form having a bottom, said inner and outer diameters thereof are formed to be approximately equal to the outer diameter of the small diameter shaft portion 31b and the outer diameter of the large diameter shaft portion 31a respectively, while outer circumferences of the cap members 32 and 33 are provided with projected keys 37 and 38 respectively.
At the bottom of the cap member 33, a concave slit 36 is formed. The cap members 32 and 33 are outwardly inserted to the small diameter shaft portions 31b and 31b respectively, ring grooves 32a and 33a of said cap members 32 and 33 being inserted into rib 31c of each small diameter shaft portion 31b to prevent the drawing out of the cap members 32 and 33, thereby being incorporated to the shaft body 31 rotatably.
In this incorporated state, the torsion bar 4 is inserted into the penetrated hole 34 to latch one end of the hook portion 41 to the penetrated hole 34 and another end of the hook portion 42 to the concave 36 of the cap portion 33 in order to incorporate therewith, and further the viscous grease is enclosed between the cap members 32 and 33 and each small diameter shaft portion 31b.
The shaft 3 thus incorporated is positioned the large diameter shaft portion 31a of the shaft body 31 in a shaft supporting portion 11a (11b) of the rotative portion 1a (1b) and further positioned the ca members 32 and 33 in bearing portions 21 (23) and 22 (24) of the fixed member 2 respectively, while each key 35, 37 and 38 is inserted into key grooves formed at a shaft supporting portion 11a (11b), a bearing portions 21 (23) and 22 (24) respectively whereby the large diameter shaft portion 31a and the cap members 32, 33 are unrotatably attached to the shaft supporting portion 11a (11b) and the bearing portion 21 (23) and 22 (24) respectively.
In the conventional slow-acting rotation shaft device thus constructed, though the rotative members 1a and 1b rotate by the torque of the torsion bar 4, this rotation can be performed with a slow speed in spite of the torque load of the torsion bar 4 due to the viscous resistance of the viscous grease at the time of this rotation.
However, the conventional slow-acting rotation shaft device is only provided a function which rotates one rotative member relatively rotates with respect to the fixed member with slow speed. Accordingly, it is necessary to provide two pieces (two shafts type) in the above switch device having two rotation members.
For this object, in the switch device having two rotative members, a space for arranging the slow-acting rotative shaft device must be secured widely. Accordingly, it is difficult to apply a slow-acting rotative shaft device to a small switch device such as a compact case for toiletries, a case for a compact disc or the like which is difficult to secure the space for arranging.
Further, this includes a problem to increase a cost for arrangement of a plurality of the slow-acting rotation shaft device.
Furthermore, this includes the following problems since in the conventional slow-acting rotation shaft device, the shaft body 31 and the cap member 33 which constitutes the shaft 3 are incorporated rotatably with respect to each other:
(1) to provide an initial torque to the torsion bar 4 is impossible at the time of assembly of the shaft 3. It is possible for the first time to provide it in the relation of the rotative members 1a, 1b and the fixed member 2 at the time of assembling the shaft 3 to the rotatably supporting portions of the rotative members 1a, 1b. Accordingly, the incorporation thereof is difficult.
(2) Although a twisting direction of the torsion bar 4 at the time of use is constrained by setting, there exists a fear that a permanent set of the torsion bar 4 will occur by a mistaken operation of the cap member 33 in the opposite direction against the above direction.
(3) Since the permanent set of the torsion bar 4 occurs by the rotation more than the maximum, rotation angle because the shaft 3 itself has no means which constrains a rotation angle, it is necessary to provide the above means to the rotative members 1a, 1b and the fixed member 2, which causes a troublesome of working to the rotative members 1a and 1b and the fixed member 2.
This invention is performed in view of the above reasons. The first object is to provide a slow-acting rotation shaft device having one shaft type which is possible to control the speed in each of two rotative members and is not necessary for a large setting space. Further, a second object of this invention is to provide a slow-acting rotation shaft device which is a one-shaft type one possible to provide an initial torque to the torsion bar at the time of assembly of the shaft and can prevent a mistaken operation and the rotation more than the maximum, rotation angle by shaft itself.